Abstract/Summary

Hybridisation between introduced and native species is an increasingly important
issue concerning environmental stakeholders because it decreases genetic integrity of native stocks.
However, hybridisation could also happen between non-native species even if these species belong
to different genera. Our study illustrates this particular aspect of alien species invasion with the
attempt of artificial hybridisation between sunbleak Leucaspius delineatus and topmouth gudgeon
Pseudorasbora parva, both recent additions to the freshwater fish fauna of England. The crossed
fertilisation of L. delineatus ova with P. parva sperm lead to viable eggs with a very high hatching rate
of 86% although hybrids failed to develop beyond the 1st larval step. Early morphological development
of these hybrids was quantified and compared to the early development of the pure bred species.